Field of the Invention
The present invention relates to a probe used for eddy current testing used for non-destructive testing.
Description of the Related Art
As a non-destructive testing method for metals, an Eddy Current Testing (ECT) is known. In this flaw detection method, an eddy current is generated on a surface of a test object by an exciter coil, and changes in a voltage (or changes in an impedance) of a detector coil caused by the influence of this eddy current are observed to detect a flaw developed in the test object.
The present inventors have proposed an eddy current testing probe that can accurately detect a flaw, in Japanese Patent No. 3343860. The eddy current testing probe of Japanese Patent No. 3343860 has an advantage of accurately detecting a flaw on a specimen based on a voltage difference generated between detector coils resulting from magnetic fluxes, even if a diagonal lift-off change occurs, which is a difference between distances from the detector coils to the test object.
In the eddy current testing probe of Japanese Patent No. 3343860, an exciter coil is arranged over the detector coils. In addition, there is distinction between up and down assuming that the test object is placed under the detector coil. Therefore, the eddy current testing probe of Japanese Patent No. 3343860 has a thickness of those of the detector coils and the exciter coil, and the probe may not be used in very narrow places.
The present invention is made based on such a technical problem, and has an object to provide an eddy current testing probe that can have a small thickness while having detector coils and exciter coils.